--- a/svgui/pyjs/build.py	Tue Oct 09 11:43:39 2018 +0300
+++ b/svgui/pyjs/build.py	Tue Oct 09 11:56:45 2018 +0300
@@ -45,7 +45,7 @@
 
 
 # .cache.html files produces look like this
-CACHE_HTML_PAT = re.compile('^[a-z]*.[0-9a-f]{32}\.cache\.html$')
+CACHE_HTML_PAT = re.compile(r'^[a-z]*.[0-9a-f]{32}\.cache\.html$')
 
 # ok these are the three "default" library directories, containing
 # the builtins (str, List, Dict, ord, round, len, range etc.)